The proposed research seeks to determine variables important in the loss or preservation of ganglion cells of the retina after cortical lesions as a consequence of transneuronal retrograde degeneration in primates and other mammals. After longstanding cortical lesions produce such ganglion cell loss, the projection patterns of the remaining ganglion cells will be studied by autoradiographic procedures. These studies will document the conditions of ganglion cell loss, lead to a better understanding of the phenomenon of transneuronal retrograde degeneration, and provide basic information on the central connections of different cell classes of the retina.